I read that only 3 Hymac 370's were built in the late 60's (one is preserved in Scotland). Poclain made an 8 tonner in the 70's but it was thought at the time that there was no marketplace for a machine of this size. Neither of these would have had front mounted blades or indeed an offset boom. The fully hydraulic 3RB was based on 10 RB running gear & I thought it a bit heavier than 7t closer to 10t? This was made between 1962 & '67 (available to order till '69 but it is not thought that one was built post '67) It had twin gear pumps & a vane slew pump. Hughes Plant of Ironbridge ran an early one till about '74 when it was sold to a big farmer. My Dad's cousin drove it.
Another early small 360 was based on the Priestman Cub - we called it the Hydro Cub, it was mechanical in slewing & travel but had an an added Vickers vane pump to run boom, dipper, bucket, rams. Some say this was the Beaver, but others say the Beaver was the same thing but fully hydraulic like Hymac. I actually drove one as a youngster. The purely mech Cub was 7t - not sure about the hybrid machine. Smith Rodley made a hybrid Smith 14 very like the Hydro Cub, one was bought by a waterways restoration trust, so pics survive - along with some Smalley stuff they owned.
In the mid 70's Priestman & Hymac used to fight for the title of greatest UK sales in the 12t market. The heavier Priestman 160 (from '73 on) was advanced - with twin axial pumps, full servo controls, but only captured 5% of the UK market - they later back tracked & made a more budget 168S with gear pumps & direct controls. Hitachi went axial pumps late '70s. It is a matter of an idea being 'of its time' - & there are 'fashions' in plant I was told. Hymac was once the market leader in Scandinavia, you would think it would have been Priestman - both on strength & where built grounds. Local contractor C.J. Pearce ran Priestmans but would not touch Hymac, seeing them more as a 'housebuilder' machine either rightly or wrongly. UK Army ran Hymacs though.
Re 'wheelbarrow' machines the Tusker Digger Dumper was once popular, simple & low cost. Winget made a slightly better one with hydraulic stabilizers (to save the driver's back, as I found out on the Thwaites)